Attribute-Based Broadcast Encryption Scheme Made Efficient

In this paper, we describe a new broadcast encryption scheme for stateless receivers. The main difference between our scheme and the classical ones derived from the complete subtree paradigm is that the group of privileged users is described by attributes. Actually, some real applications have been described where the use of a more adaptable access structure brings more efficiency and ease of deployment. On the other side, the decryption algorithm in so far existing attribute-based encryption schemes adapted for broadcast applications is time-consuming for the receiver, since it entails the computation of a large number of pairings. This is a real drawback for broadcast applications where most of the technological constraints are on the receiver side. Our scheme can be viewed as a way to benefit at the same time from the performance of decryption of the classical broadcast schemes and the management easiness provided by the use of a more adaptable data structure based on attributes. More precisely, our scheme allows one to select or revoke users by sending ciphertexts of linear size with respect to the number of attributes, which is in general far less than the number of users. We prove that our scheme is fully collusion secure in the generic model of groups with pairing.